EXHAUST
12-04-2005, 05:26 PM
#20
Burning Brakes
when i refer to resonance i mean the sound level in the car increases to undesireable levels probably due to constructive interference of acoustic waves with something....could be a lot of things...who knows what. i need to listen to the car from the outside (with someone else driving) and see if i can hear it ....to determine if it is starting at the tailpipe or if it is coupling thru the structure of the car
12-05-2005, 06:03 AM
#21
Originally Posted by Gary R.
Don't believe ridiculous claims of added HP for a muffler change. Even if you go to tuned headers on out without other changes the gain is moot.
12-05-2005, 12:32 PM
#22
Rennlist Member
resonance. everything has a natural frequency at which natural damping forces (energy losses are great) are overcome by an increase in energy amplitude. one tries to adjust the natural frequency by means of mass or stiffness out of the normal operating range. one hears this in exhaust sysems as you increase rpm there may be an rpm setting where the combined natural frequency is hit and you get vibration in the system and significant sound. go beyond that rpm and vibration and sound amplitude from the exhaust goes down.
Last edited by stevepaa; 12-05-2005 at 04:33 PM.
12-05-2005, 12:45 PM
#23
Guest
Posts: n/a
Hey Steve, that was the best explanation I’ve ever read on "resonance", what about a simple perforation in the aft silencer, I going to drill a hole in it, to verify these reasoning’s!! Were you able align your squirters okay, sorry for not having a ruler in inches,. Send me a photo one day,. All the best,
12-05-2005, 04:50 PM
#24
Rennlist Member
Hi Marc, I need to get all the pieces before I have a chance to add the squirters. If you want to get rid of resonance, you need to find the offending piece. Have someone rev it to the resonance RPM and then go around and push with the bottom of a shoe on various parts to find it. Sometimes you can add another support strap to it and alter its frequency. Sometimes a simple addition of a metal strip welded onto it will do it. I would not expect a hole to really do much, you either need to alter the stiffness of the metal pieces or make an addition inside to affect the ascoustic waves. You may get another whistle created due to Helmhotz principle by adding a hole..
12-05-2005, 05:06 PM
#25
Burning Brakes
that gives me an idea...i have some band clamps that will fit around the muffler... (i think the resonance is the outer skin of the muffler). that should effect at least a change in the responce.
12-06-2005, 05:13 PM
#27
Burning Brakes
band clamp around the middle of the muffler seems to have reduced the amplitude. it did not change the frequency...at least it seems so. it's a subtle change but i think it did change.
